Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek
[7] oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "none" "daily" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "oncePerWeek" "none"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily severalPerWeek severalPerWeek none oncePerWeek daily
[7] oncePerWeek severalPerWeek oncePerWeek daily daily severalPerWeek
[13] daily severalPerWeek daily none severalPerWeek oncePerWeek
[19] none daily oncePerWeek none daily daily
[25] severalPerWeek oncePerWeek severalPerWeek oncePerWeek none daily
[31] none none none severalPerWeek severalPerWeek none
[37] severalPerWeek none severalPerWeek severalPerWeek daily daily
[43] oncePerWeek daily daily none none oncePerWeek
[49] severalPerWeek none daily none oncePerWeek none
[55] daily severalPerWeek severalPerWeek severalPerWeek severalPerWeek none
[61] oncePerWeek severalPerWeek daily severalPerWeek none none
[67] oncePerWeek oncePerWeek oncePerWeek none none oncePerWeek
[73] oncePerWeek none daily oncePerWeek none severalPerWeek
[79] daily oncePerWeek none daily severalPerWeek severalPerWeek
[85] oncePerWeek none oncePerWeek oncePerWeek severalPerWeek oncePerWeek
[91] none oncePerWeek severalPerWeek severalPerWeek oncePerWeek oncePerWeek
[97] severalPerWeek none oncePerWeek oncePerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 26
2 oncePerWeek 27
3 severalPerWeek 27
4 daily 20
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 20
2 severalPerWeek 27
3 oncePerWeek 27
4 none 26